#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
std::vector<double> nums, sum, lazy, square;
void up(int i) {
    sum[i] = sum[i << 1] + sum[(i << 1) | 1];
    square[i] = square[i << 1] + square[(i << 1) | 1];
}
void build(int i, int l, int r) {
    lazy[i] = 0;
    if (l == r) {
        sum[i] = nums[l];
        square[i] = nums[l] * nums[l];
        return;
    }
    int m = l + ((r - l) >> 1);
    build(i << 1, l, m);
    build((i << 1) | 1, m+1, r);
    up(i);
}
void down(int i, int l, int r) {
    int m = l + ((r - l) >> 1);
    if (lazy[i]) {
        lazy[i << 1] += lazy[i];
        lazy[(1 << 1) | 1] += lazy[i];
        square[i << 1] += 2.0 * sum[i << 1] * lazy[i] + (m-l+1) * lazy[i] * lazy[i];
        square[(i << 1) | 1] += 2.0 * sum[(i << 1) | 1] * lazy[i] + (r - m) * lazy[i] * lazy[i];
        sum[i << 1] += lazy[i] * (m - l + 1);
        sum[(i << 1) | 1] += lazy[i] * (r - m);
        lazy[i] = 0;
    }
}
void add(int i, int l, int r, int ql, int qr, double val) {
    if (ql <= l && r <= qr) {
        lazy[i] += val;
        square[i] += 2.0 * sum[i] * val + (r-l+1) * val * val;
        sum[i] += val * (r - l + 1);
        return;
    }
    down(i, l, r);
    int m = l + ((r - l) >> 1);
    if (m >= ql) add(i << 1, l, m, ql, qr, val);
    if (m < qr) add((i << 1) | 1, m + 1, r, ql, qr, val);
    up(i);
}
double querySum(int i, int l, int r, int ql, int qr) {
    if (ql <= l && r <= qr) {
        return sum[i];
    }
    down(i, l, r);
    int m = l + ((r - l) >> 1);
    double res = 0;
    if (m >= ql) res += querySum(i << 1, l, m, ql, qr);
    if (m < qr) res += querySum((i << 1) | 1, m + 1, r, ql, qr);
    return res;
}
double querySquare(int i, int l, int r, int ql, int qr) {
    if (ql <= l && r <= qr) {
        return square[i];
    }
    down(i, l, r);
    int m = l + ((r - l) >> 1);
    double res = 0;
    if (m >= ql) res += querySquare(i << 1, l, m, ql, qr);
    if (m < qr) res += querySquare((i << 1) | 1, m + 1, r, ql, qr);
    return res;
}

int main()
{
    int m, n;
    std::cin >> n >> m;
    nums.resize(n + 1);
    sum.resize(4 * n);
    square.resize(4 * n);
    lazy.resize(4 * n);
    for (int i = 1; i <= n; ++i) {
        std::cin >> nums[i];
    }
    build(1, 1, n);
    double k, su, sq;
    //std::cout << std::fixed << std::setprecision(4);
    for (int i = 0, c, x, y; i < m; ++i) {
        std::cin >> c >> x >> y;
        if (c == 1) {
            std::cin >> k;
            add(1, 1, n, x, y, k);
        }
        else if (c == 2) {
            su = (double)querySum(1, 1, n, x, y) / (y - x + 1);
            //std::cout << su << std::endl;
            printf("%.4lf\n", su);
        }
        else {
            su = (double)querySum(1, 1, n, x, y) / (y - x + 1);
            sq = (double)querySquare(1, 1, n, x, y) / (y - x + 1);
            //std::cout << sq - su * su << std::endl;
            printf("%.4lf\n", sq - su*su);
        }
    }
    return 0;
}